The present disclosure relates to semiconductor integrated circuits (ICs), and more particularly, to flip-flop circuits used therein.
Through the development of ICs, various electronic devices including computers have the characteristics of high reliability, high speed, low power and miniaturization. As such electronic devices become more and more highly integrated, the complexity of circuits increases. For example, a very large scale IC (VLSI) can integrate more than one hundred thousand transistors in one chip. Thus, the implementation of a complicated IC is considered to be an important factor in determining the performance of an IC.
In particular, in an application specific IC (ASIC), a standard cell is used as an efficient logic device. The standard cell typically includes multiple transistors and provides logic functions (AND, OR, XOR and the like) and storage functions (Flip-Flop, latch and the like). Also, various standard cells that perform different functions can constitute a standard cell library.
A flip-flop that performs a storage function is a basic circuit which can maintain one bit information in two stable states using a structure that has a delayed output with respect to an input and that feeds back to the input. There are various kinds of flip-flops such as a data or delay (D) flip-flop, a reset-set (RS) flip-flop, a JK flip-flop and a toggle (T) flip-flop.
Flip-flops have a high processing speed and are mainly used in small devices requiring high speed, such as registers of a microprocessor. However, since a flip-flop has a complicated structure to maintain one bit information, the cost per one bit increases as integration becomes high. Therefore, a need exists for flip-flop circuits that can be effective for use in highly integrated ICs.